5 Answers
5

It gets publicity - sometimes through deliberate advocacy (marketing), sometimes through just seeing it in action.

There cost of adoption is outweighed by the benefits.

Developers who are already happy with MVC-and-friends are unlikely to go looking for alternatives unless they see flaws in their existing approach. I assume MVC and its better-known variants already meets the need to separate concerns for many developers.

Even if they go looking they are unlikely to find it unless others are using it and writing about it. In the case of PAC, I would guess that most develpers are simply unaware of the approach (I hadn't heard of it until I read this question).

Even if they find it, they won't use it unless the benefits outweigh the costs of adoption. Numerous frameworks aleady incorporate an MVC-based approach, making that cost quite high for many developers.

Most people knocking out a web application these days will be following a well-trodden path using design decisions provided by the designers of some web framework or other. In the Java world SpringMVC is a popular choice (perhaps because there is no alternative, PAC or otherwise to muddy the waters). Other developers understand and are happy with the benefits provided by this approach and don't really see a need to change.

MVC works well, is easy to understand and, when used effectively, reduces the complexity of the web application code.

To move from MVC to PAC, what we have to do is changing the directory structure. MVC follows a horizontal approach while PAC follows vertical. But logically an application can be thought of following both simultaneously.